Typhoid Fever: Cause and Symptoms
Typhoid fever is caused by Salmonella enterica subspecies enterica serovar Typhi (S. Typhi) and is characterized by fever, headache, lethargy, malaise, and abdominal pain, often followed by hepatosplenomegaly and stupor. 1
Causative Agent
Typhoid fever is caused by infection with Salmonella enterica serovar Typhi, a gram-negative bacillus that exclusively infects humans. Key characteristics of the pathogen include:
- S. Typhi is a human-specific pathogen with no animal reservoir 2
- Transmission occurs through the fecal-oral route via contaminated food or water 1, 3
- The bacterium enters the body through the gastrointestinal tract 1
Mode of Transmission
The primary modes of transmission include:
- Consumption of food or water contaminated with feces from infected individuals 3
- Contact with asymptomatic carriers who continue to shed the bacteria 4
- Laboratory exposure to S. Typhi cultures 1
Typhoid fever is endemic in many parts of the world, with highest incidence in:
- South and Southeast Asia
- Central and South America
- Africa
- Central and East Asia
- Oceania 1
Clinical Presentation and Symptoms
Typhoid fever typically presents with:
Early symptoms (first week):
- Insidious onset of sustained fever
- Headache
- Lethargy and malaise
- Anorexia (loss of appetite)
- Relative bradycardia (slow pulse despite fever)
- Abdominal pain 1
Later symptoms:
- Hepatosplenomegaly (enlarged liver and spleen)
- Stupor (altered mental status)
- Constipation (more common) or diarrhea 1
- Nonproductive cough 1
Important clinical notes:
- Diarrhea is an uncommon feature, despite the gastrointestinal portal of entry 1
- Many mild and atypical infections occur 1
- If left untreated, intestinal, neuropsychiatric, and other complications may develop 5
- Extraintestinal complications can affect multiple systems:
- Central nervous system
- Cardiovascular system
- Pulmonary system
- Hepatobiliary system 2
Risk Factors
The risk for typhoid fever is highest for:
- Travelers to endemic areas, particularly South and Southeast Asia 1
- People visiting friends and relatives in endemic countries 1
- Those consuming potentially contaminated food and water in rural areas off usual tourist routes 1
- Individuals with continued household contact with documented typhoid carriers 1
- Laboratory workers who frequently work with S. Typhi 1
- People living in areas with poor sanitation, improper drainage systems, and scarcity of potable water 3
Diagnostic Considerations
Diagnosis of typhoid fever requires:
- Isolation of S. Typhi from blood, stool, or other clinical specimen 1
- Blood cultures have the highest yield within the first week of symptoms 5
- Serologic tests alone (like the Widal test) are not sufficient for diagnosis 1, 6
Prevention
Preventive measures include:
- Careful selection of food and water in endemic areas 1
- Vaccination for travelers to high-risk areas 1
- Two types of vaccines are available:
- Oral live-attenuated Ty21a vaccine
- Capsular polysaccharide parenteral vaccine 1
Clinical Pitfalls to Avoid
- Failing to consider typhoid fever in febrile travelers returning from endemic areas 1
- Overlooking the possibility of typhoid fever in patients with fever but without diarrhea 1
- Relying solely on serologic tests for diagnosis without culture confirmation 1, 6
- Not recognizing increasing antimicrobial resistance patterns, particularly to fluoroquinolones in South and Southeast Asia 1, 6
Typhoid fever remains a significant public health challenge globally, with approximately 11-21 million cases occurring annually worldwide, accounting for 120,000-160,000 deaths 2. Early recognition of symptoms and prompt appropriate treatment are essential to prevent complications and reduce mortality.